Tailored Materials for Surface-Enhanced Raman Spectroscopy
type: CreativeWork
description: Surface-enhanced Raman spectroscopy (SERS) is a useful analytical tool that has grown in popularity since its discovery 40 years ago. Presently, a large number of materials are used as SERS substrates, including thiol-functionalised nanoparticles which form a large class of SERS-active materials as they are able to form selfassembled monolayers on the surface of a substrate and provide surface properties that may be tailored by altering the adsorbed thiol. Mixtures of thiols have been used to provide a wider range of surface properties but there is considerable uncertainty surrounding the mechanism of thiol adsorption, and so the aim of this project has been to develop an understanding of the kinetics and mechanism of the thiol adsorption process, specifically the co-adsorption of pairs of thiols onto silver nanoparticles. Normally the chosen thiols are added to the nanoparticle suspension followed by an aggregating agent which will create coupled surface plasmons leading to an enhanced signal. However, any changes in the SERS signal with time will be due to a combination of increasing population of thiol at the surface and the enhancement factor of the particle aggregates as aggregation progresses. It was therefore necessary to find conditions under which the aggregates would provide a stable enhancement factor and although a large number of colloid/salt combinations produced rapid aggregation followed by precipitation and subsequent loss of SERS signal, it was found that by using low concentrations of MgSO4, reasonably strong SERS enhancing aggregates which gave stable signals over 10 minutes could be generated. Once this method of preparing stable pre-aggregated colloids had been established, the adsorption of single thiols was monitored over time using SERS. Although using pre-aggregation generally reduced the signal levels making it difficult to monitor thiols with low scattering cross-sections, such as aliphatic thiols, it was still possible to use the batch s…
abstract: Surface-enhanced Raman spectroscopy (SERS) is a useful analytical tool that has grown in popularity since its discovery 40 years ago. Presently, a large number of materials are used as SERS substrates, including thiol-functionalised nanoparticles which form a large class of SERS-active materials as they are able to form selfassembled monolayers on the surface of a substrate and provide surface properties that may be tailored by altering the adsorbed thiol. Mixtures of thiols have been used to provide a wider range of surface properties but there is considerable uncertainty surrounding the mechanism of thiol adsorption, and so the aim of this project has been to develop an understanding of the kinetics and mechanism of the thiol adsorption process, specifically the co-adsorption of pairs of thiols onto silver nanoparticles. Normally the chosen thiols are added to the nanoparticle suspension followed by an aggregating agent which will create coupled surface plasmons leading to an enhanced signal. However, any changes in the SERS signal with time will be due to a combination of increasing population of thiol at the surface and the enhancement factor of the particle aggregates as aggregation progresses. It was therefore necessary to find conditions under which the aggregates would provide a stable enhancement factor and although a large number of colloid/salt combinations produced rapid aggregation followed by precipitation and subsequent loss of SERS signal, it was found that by using low concentrations of MgSO4, reasonably strong SERS enhancing aggregates which gave stable signals over 10 minutes could be generated. Once this method of preparing stable pre-aggregated colloids had been established, the adsorption of single thiols was monitored over time using SERS. Although using pre-aggregation generally reduced the signal levels making it difficult to monitor thiols with low scattering cross-sections, such as aliphatic thiols, it was still possible to use the batch s…
author: McCabe, Hannah
language: eng
date published: 2019
date modified: 2026-07-24T03:54:59Z
provider: Queen's University Belfast
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Queen's University Belfast